Methods for making composite structures that are used throughout the boating, automobile, swimming pool, and bathtub industries are known in the art. These conventional methods for making composite structures typically produce composite structures that include a first, or top, layer of styrenated polyester. In the convention methods, the first-layer of styrenated polyester is applied to a mold substrate, and during the application of the first-layer, large quantities of styrene monomers, which are considered volatile organic compounds (VOCs), are emitted into the surrounding environment. Emission of styrene monomers is highly undesirable for environmental, health, and safety reasons. Furthermore, large quantities of other VOCs, such as methyl ethyl ketone, are also typically emitted in these conventional methods. Emission of these other VOCs occurs during the application and the cross-linking of the various layers of the composite structure, including the styrenated polyester first-layer. As with emission of the styrene monomers, emission of these other VOCs is also undesirable for environmental, health, and safety reason.
Furthermore, it is known in the art that styrenated polyesters are excessively brittle, and because the first, or top, layer of these composite structures include styrenated polyesters, the method for making the composite structures of the prior art produce composite structures that typically suffer from cracking and chipping defects due to this excessive brittleness. Such defects become particularly apparent during shipping and handling, during transportation, and even during use of the composite structures. Finally, the methods of making the composite structures of the prior art also utilize various aromatic components, such as aromatic isocyanates and styrene, which are components that are unstable over exposure to ultraviolet light. As such, these methods are deficient because they produce composite structures that are unstable over exposure to ultraviolet light.
Due to the inefficiencies identified in the methods for making the composite structures of the prior art, it is desirable to provide a novel method for making a durable composite structure that includes a top layer that does not emit VOCs during application to the mold substrate and that utilizes aliphatic components such that the top layer, and therefore the entire composite structure, is stable under exposure to ultraviolet light.